Oxide-semiconductor interfaces are the workhorse of the semiconductor industry. The requirements for gate quality oxide-semiconductor structures are manifold; among the requirements for functional accumulation/inversion mode devices is a low interface state density D.sub.it &lt;10.sup.11 cm.sup.-2 eV.sup.-1. In silicon technology, interface states of as processed SiO.sub.2 --Si interfaces (N.sub.it .congruent.10.sup.12 cm.sup.-2) are ascribed to silicon dangling bonds such as P.sub.b centers. It is well known in the art, that the interface state density of an as processed structure can be drastically reduced to as low as 10.sup.8 cm.sup.-2 by annealing in a hydrogen (H.sub.2) or more recently, in a deuterium (D.sub.2) containing atmosphere.
For compound semiconductors, functional oxide-III-V compound semiconductor interfaces are fabricated by in situ deposition of gallium oxide molecules on GaAs based epitaxial layers while maintaining an ultra-high vacuum (UHV), see for instance U.S. Pat. No. 5,451,548 entitled "Electron beam deposition of gallium oxide thin films using a single purity crystal source", issued Sep. 19, 1995, M. Hunt et al., Appl. Phys. Lett., vol. 68, 1099 (1996), Appl. Phys. Lett., vol. 68, 3605 (1996), and Appl. Phys. Lett., vol. 69, 302 (1996). For as deposited structures, an interface state density N.sub.it .congruent.1-2.times.10.sup.11 cm.sup.-2 was achieved with a minimum of D.sub.it .congruent.3-4.times.10.sup.10 cm.sup.-2 eV.sup.-1 around midgap. More recent measurements indicated a D.sub.it in the upper 10.sup.11 cm.sup.-2 eV.sup.-1 range close to the band edges. Device performance is affected since the energy range in the vicinity of the band edges is of crucial importance for accumulation/inversion type devices.
For GaAs, it has been speculated that passivation effects, for example due to H.sub.2, could reduce the surface state density to acceptable levels as well, see for instance F. Capasso et al., J. Electrochem. Soc., vol. 129, 821 (1982). However, experimental proof for the hypothesis could not be provided and the role of hydrogen has been diminished to cleaning of GaAs surfaces only, see for instance U.S. Pat. No. 4,859,253 entitled "Method for passivating a compound semiconductor surface and device having improved semiconductor-insulator interface", issued Aug. 22, 1989.
Accordingly, it would be highly desirable to provide new methods of passivation of interface states which overcome these problems.
It is a purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces.
It is another purpose of the present invention to provide a new and improved method for passivating interface states at oxide-GaAs interfaces.
It is still another purpose of the present invention to provide a new and improved method for passivating interface states at Ga.sub.2 O.sub.3 --GaAs interfaces.
It is yet another purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces using molecular, atomic, or isotopic species.
It is a further purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces wherein said molecular, atomic, or isotopic species are applied before oxide deposition in ultra-high vacuum.
It is still a further purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces wherein said molecular, atomic, or isotopic species are applied during interruption of oxide deposition in ultra-high vacuum (preferentially after oxide surface coverage of a submonolayer, a monolayer, or a few monolayers).
It is yet a further purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces wherein said molecular, atomic, or isotopic species are applied during oxide deposition in ultra-high vacuum.
It is still a further purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces wherein said molecular, atomic, or isotopic species are applied after completion of oxide deposition.
It is yet a further purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces wherein said molecular, atomic, or isotopic species are applied before or after any processing steps of the as deposited interface structure.
It is still a further purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces wherein said molecular, atomic, or isotopic species are molecular/atomic hydrogen or molecular/atomic deuterium.
It is yet a further purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces wherein said molecular, atomic, or isotopic species are molecular or atomic nitrogen.
It is still a further purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces such that the interface state density, in particular in the vicinity of the band edges, is significantly reduced.
It is yet a further purpose of the present invention to provide a new and improved method for passivating interface states at oxide-compound semiconductor interfaces such that the performance of accumulation/inversion type devices is not affected.
It is still a further purpose of the present invention to provide a new and improved method of manufacturing a gate quality oxide-compound semiconductor structure which is relatively easy to fabricate and use.
It is yet a further purpose of the present invention to provide a new and improved method of manufacturing a gate quality Ga.sub.2 O.sub.3 -compound semiconductor structure which is relatively easy to fabricate and use.